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Bateman A.W.,University of Alberta | Anholt B.R.,Bamfield Marine Sciences Center
Journal of Evolutionary Biology | Year: 2017

R. A. Fisher predicted that individuals should invest equally in offspring of both sexes, and that the proportion of males and females produced (the primary sex ratio) should evolve towards 1:1 when unconstrained. For many species, sex determination is dependent on sex chromosomes, creating a strong tendency for balanced sex ratios, but in other cases, multiple autosomal genes interact to determine sex. In such cases, the maintenance of multiple sex-determining alleles at multiple loci and the consequent among-family variability in sex ratios presents a puzzle, as theory predicts that such systems should be unstable. Theory also predicts that environmental influences on sex can complicate outcomes of genetic sex determination, and that population structure may play a role. Tigriopus californicus, a copepod that lives in splash-pool metapopulations and exhibits polygenic and environment-dependent sex determination, presents a test case for relevant theory. We use this species as a model for parameterizing an individual-based simulation to investigate conditions that could maintain polygenic sex determination. We find that metapopulation structure can delay the degradation of polygenic sex determination and that periods of alternating frequency-dependent selection, imposed by seasonal fluctuations in environmental conditions, can maintain polygenic sex determination indefinitely. © 2017 European Society For Evolutionary Biology.


McGaw I.J.,Memorial University of Newfoundland | McGaw I.J.,Bamfield Marine Sciences Center | Curtis D.L.,Canadian Department of Fisheries and Oceans
Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology | Year: 2013

This article reviews the mechanical processes associated with digestion in decapod crustaceans. The decapod crustacean gut is essentially an internal tube that is divided into three functional areas, the foregut, midgut, and hindgut. The foregut houses the gastric mill apparatus which functions in mastication (cutting and grinding) of the ingested food. The processed food passes into the pyloric region of the foregut which controls movement of digesta into the midgut region and hepatopancreas where intracellular digestion takes place. The movements of the foregut muscles and gastric mill are controlled via nerves from the stomatogastric ganglion. Contraction rates of the gastric mill and foregut muscles can be influenced by environmental factors such as salinity, temperature, and oxygen levels. Gut contraction rates depend on the magnitude of the environmental perturbation and the physiological ability of each species. The subsequent transit of the digesta from the foregut into the midgut and through the hindgut has been followed in a wide variety of crustaceans. Transit rates are commonly used as a measure of food processing rates and are keys in understanding strategies of adaptation to trophic conditions. Transit times vary from as little as 30 min in small copepods to over 150 h in larger lobsters. Transit times can be influenced by the size and the type of the meal, the size and activity level of an animal and changes in environmental temperature, salinity and oxygen tension. Ultimately, changes in transit times influence digestive efficiency (the amount of nutrients absorbed across the gut wall). Digestive efficiencies tend to be high for carnivorous crustaceans, but somewhat lower for those that consume plant material. A slowing of the transit rate allows more time for nutrient absorption but this may be confounded by changes in the environment, which may reduce the energy available for active transport processes. Given the large number of articles already published on the stomatogastric ganglion and its control mechanisms, this area will continue to be of interest to scientists. There is also a push towards studying animals in a more natural environment or even in the field and investigation of the energetic costs of the components of digestion under varying biotic and environmental conditions will undoubtedly be an area that expands in the future. © 2012 Springer-Verlag Berlin Heidelberg.


Neufeld C.J.,University of Alberta | Neufeld C.J.,Bamfield Marine Sciences Center
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution | Year: 2011

Traits can evolve both in response to direct selection and in response to indirect selection on other linked traits. Although the evolutionary significance of coupled traits (e.g., through shared components of developmental pathways, or through competition for shared developmental resources) is now well accepted, we know comparatively little about how developmental coupling may restrict the independent responses of two or more phenotypically plastic traits in response to conflicting environmental cues. Such studies are important because coupled development, if present, could act as an important limit to the evolution of functionally independent plasticity in multiple traits. I tested whether developmental coupling can restrict the direction of plastic responses by studying how penis form and leg form-both highly plastic traits of barnacles-varied in response to differences in conspecific density and water velocity. Penis length and leg length in Balanus glandula varied in parallel with variation in wave-exposure but varied in opposite directions with variation in conspecific density. This study represents one of the rare tests of developmental coupling between multiple (demonstrably adaptive) plastic traits: Barnacle legs and penises appear to exhibit modular development that can respond concurrently-yet in independent directions-to conflicting environmental cues. Copyright © 2011 Wiley-Liss, Inc., A Wiley Company.


Wood C.M.,McMaster University | Wood C.M.,Bamfield Marine Sciences Center | Nawata C.M.,McMaster University | Nawata C.M.,Bamfield Marine Sciences Center
Journal of Experimental Biology | Year: 2011

Steelhead rainbow trout acclimated to either freshwater (FW) or seawater (SW) were exposed to high environmental ammonia (HEA, 1000μmoll -1 NH 4HCO 3, pH7.8-8.0) for 24h. SW trout restored ammonia excretion more rapidly (3-6h versus 9-12h in FW), despite higher production rates and lower plasma pH. Plasma total ammonia levels stabilized at comparable levels below the external HEA concentration, and blood acid-base disturbances were small at both salinities. The electrochemical gradients for NH 4 + entry (FNH 4 +) were the same in the two salinities, but only because FW trout allowed their transepithelial potential to rise by -15mV during HEA exposure. Elevation of plasma [cortisol] during HEA exposure was more prolonged in SW fish. Plasma [glucose] increased in SW, but decreased in FW trout. Plasma [urea-N] also decreased in FW, in concert with elevated urea transporter (UT) mRNA expression in the gills. Of 13 branchial transporters, baseline mRNA expression levels were higher for Rhcg1, NHE2, NKCC1a and UT, and lower for NBC1 and NKA-1a in SW trout, whereas NKA-1b, NHE3, CA2, H +-ATPase, Rhag, Rhbg and Rhcg2 did not differ. Of the Rh glycoprotein mRNAs responding to HEA, Rhcg2 was greatly upregulated in both FW and SW, Rhag decreased only in SW and Rhcg1 decreased only in FW. H+-ATPase mRNA increased in FW whereas NHE2 mRNA increased in SW; NHE3 did not respond, and V-type H +-ATPase activity declined in SW during HEA exposure. Branchial Na +,K +- ATPase activity was much higher in SW gills, but could not be activated by NH 4 +. Overall, the more effective response of SW trout was explained by differences in physical chemistry between SW and FW, which greatly reduced the plasma NH 3 tension gradient for NH 3 entry, as well as by the higher [Na +] in SW, which favoured Na +-coupled excretion mechanisms. At a molecular level, responses in SW trout showed subtle differences from those in FW trout, but were very different than in the SW pufferfish. Upregulation of Rhcg2 appears to play a key role in the response to HEA in both FW and SW trout, and NH 4 + does not appear to move through Na +,K +-ATPase. © 2011. Published by The Company of Biologists Ltd.


Nienhuis S.,Bamfield Marine Sciences Center
Proceedings. Biological sciences / The Royal Society | Year: 2010

As CO(2) levels increase in the atmosphere, so too do they in the sea. Although direct effects of moderately elevated CO(2) in sea water may be of little consequence, indirect effects may be profound. For example, lowered pH and calcium carbonate saturation states may influence both deposition and dissolution rates of mineralized skeletons in many marine organisms. The relative impact of elevated CO(2) on deposition and dissolution rates are not known for many large-bodied organisms. We therefore tested the effects of increased CO(2) levels--those forecast to occur in roughly 100 and 200 years--on both shell deposition rate and shell dissolution rate in a rocky intertidal snail, Nucella lamellosa. Shell weight gain per day in live snails decreased linearly with increasing CO(2) levels. However, this trend was paralleled by shell weight loss per day in empty shells, suggesting that these declines in shell weight gain observed in live snails were due to increased dissolution of existing shell material, rather than reduced production of new shell material. Ocean acidification may therefore have a greater effect on shell dissolution than on shell deposition, at least in temperate marine molluscs.


Starko S.,Bamfield Marine Sciences Center | Martone P.T.,Bamfield Marine Sciences Center
New Phytologist | Year: 2016

Biomass allocation patterns have received substantial consideration, leading to the recognition of several 'universal' interspecific trends. Despite efforts to understand biomass partitioning among embryophytes, few studies have examined macroalgae that evolved independently, yet function ecologically in much the same ways as plants. Kelps allocate photosynthate among three organs (the blade(s), stipe(s) and holdfast) that are superficially convergent with organs of land plants, providing a unique opportunity to test the limits of 'universal' trends. In this study, we used an allometric approach to quantify interspecific biomass partitioning patterns in kelps and assess whether embryophyte-based predictions of biomass scaling can be applied to marine macrophytes that lack root-to-leaf hydraulic transport. Photosynthetic area and dry mass were found to scale to approximately the 3/4 power and kelp biomass allocation patterns were shown to match closely to empirical measures of allometric scaling among woody plants. Larger kelp species were found to have increased relative stipe and holdfast mass than smaller species, highlighting important consequences of size for marine macroalgae. Our study provides insights into the evolution of size in the largest marine macrophytes and corroborates previous work suggesting that the morphology of divergent lineages of photoautotrophs may reflect similar selective pressures. © 2016 New Phytologist Trust.


Marshall W.L.,University of British Columbia | Marshall W.L.,Bamfield Marine Sciences Center | Berbee M.L.,University of British Columbia | Berbee M.L.,Bamfield Marine Sciences Center
Molecular Biology and Evolution | Year: 2010

We use population genetics to detect the molecular footprint of a sexual cycle, of a haploid vegetative state, and of lack of host specificity in Pseudoperkinsus tapetis, a marine unicellular relative of the animals. Prior to this study, complete life cycles were not known for any of the unicellular lineages sharing common ancestry with multicellular animals and fungi. We established the first collection of conspecific cultures of any member from the unicellular opisthokont lineage ichthyosporea, isolating 126 cultures of P. tapetis from guts of marine invertebrates ranging from clams to sea cucumbers. We sequenced fragments of the elongation factor alpha-like (EFL) and heat-shock protein 70 (HSP70) genes for a subset of our isolates. Absence of heterozygotes from the EFL locus in 52 isolates provided evidence for haploidy. Phylogenetic incongruence and a lack of support for linkage between two loci from 34 sequenced isolates signified a history of recombination consistent with a sexual cycle. Shared haplotypes in different invertebrate species showed that P. tapetis was not host specific. Based on estimates of the frequency of sex and on observations of cultures, we propose that P. tapetis is transmitted between hosts via asexual endospores. New protists are continually being discovered, and, as this study illustrates, analysis of culturable collections from natural habitats can transform a species from a near unknown to a model system for better understanding the evolution of life histories. © 2010 The Author.


McGaw I.J.,Bamfield Marine Sciences Center | Whiteley N.M.,Bangor University
Journal of Thermal Biology | Year: 2012

The effects of temperature acclimation and acute temperature change were investigated in postprandial green shore crabs, Carcinus maenas. Oxygen uptake, gut contractions and transit rates and digestive efficiencies were measured for crabs acclimated to either 10°C or 20°C and subsequently exposed to treatment temperatures of 5, 15, or 25°C. Temperature acclimation resulted in a partial metabolic compensation in unfed crabs, with higher oxygen uptake rates measured for the 10°C acclimated group exposed to acute test temperatures. The Q 10 values were higher than normal, probably because the acute temperature change prevented crabs from fully adjusting to the new temperature. Both the acclimation and treatment temperature altered the characteristics of the specific dynamic action (SDA). The duration of the response was longer for 20°C acclimated crabs and was inversely related to the treatment temperature. The scope (peak oxygen consumption) was also higher for 20°C acclimated crabs with a trend towards an inverse relationship with treatment temperature. Since the overall SDA (energy expenditure) is a function of both duration and scope, it was also higher for 20°C acclimated crabs, with the highest value measured at the treatment temperature of 15°C. The decline in total SDA after acute exposure to 5 and 25°C suggests that both cold stress and limitations to oxygen supply at the temperature extremes could be affecting the SDA response. The contractions of the pyloric sac of the foregut region function to propel digesta through the gut, and contraction rates increased with increasing treatment temperature. This translated into faster transit rates with increasing treatment temperatures. Although pyloric sac contractions were higher for 20°C acclimated crabs, temperature acclimation had no effect on transit rates. This suggests that a threshold level in pyloric sac contraction rates needs to be reached before it manifests itself on transit rates. Although there was a correlation between faster transit times and the shorter duration of the SDA response with increasing treatment temperature, transit rates do not make a good proxy for calculating the SDA characteristics. The digestive efficiency showed a trend towards a decreasing efficiency with increasing treatment temperature; the slower transit rates at the lower treatment temperatures allowing for more efficient nutrient absorption. Even though metabolic rates of 10°C acclimated crabs were higher, there was no effect of acclimation temperature on digestive efficiency. This probably occurred because intracellular enzymes and digestive enzymes are modulated through different control pathways. These results give an insight into the metabolic and digestive physiology of Carcinus maenas as it makes feeding excursions between the subtidal and intertidal zones. © 2012.


Kucera H.,University of New Brunswick | Kucera H.,Bamfield Marine Sciences Center | Saunders G.W.,University of New Brunswick
Journal of Phycology | Year: 2012

The Bangiales is a diverse order consisting of 28 species in Canada. Morphological simplicity and similarity among species has led to taxonomic confusion and the need for molecular techniques for species identification. This study is the first to employ the standardized DNA barcode marker COI-5P in a broad floristic survey of the Bangiales in Canadian marine waters. A total of 37 species were ultimately sequenced, 29 of which occurred in Canada. Molecular results led to the synonymization of Wildemania cuneiformis with W. amplissima, as well as the description of two new species: Porphyra corallicola sp. nov. and Pyropia peggicovensis sp. nov., and discovery of another five putative new species. Comparison of the performance of COI-5P as a species identification tool relative to rbcL (large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase) and the UPA (universal plastid amplicon) revealed that, although each marker had strengths and weaknesses, the COI-5P showed the highest species-discriminatory power due to its high level of interspecific variation. The rbcL was further used to place the new species into a phylogenetic context, whereas UPA was not recommended for species identification in the Bangiales owing to within-individual heterogeneity between the two copies present in the plastid genomes in some lineages. © 2012 Phycological Society of America.


Hamilton P.T.,University of Victoria | Richardson J.M.L.,University of Victoria | Anholt B.R.,University of Victoria | Anholt B.R.,Bamfield Marine Sciences Center
Freshwater Biology | Year: 2012

Amphibians are in decline, and the disease chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has been repeatedly implicated throughout the world. This chytrid reproduces via an infectious, motile zoospore stage that remains viable for weeks in the water column. Daphnia is a keystone zooplankton grazer in intact freshwater ecosystems, whose importance to amphibians may be overlooked. As an efficient grazer, Daphnia can suppress chytrid epidemics by consuming zoospores and may therefore play a role in Bd infection dynamics. Daphnia may also have important effects on tadpoles by mediating the properties of pond food webs. We tested the role of Daphnia in outdoor mesocosms containing the tadpoles of red-legged frogs (Rana aurora) infected with Bd. We also tested the ability of Daphnia to filter Bd from the water column in laboratory microcosms. In the water of microcosms, Daphnia dramatically decreased the number of Bd genomic equivalents detectable using quantitative PCR. Bd genomic equivalents fell below the limit of detection at very high (>1DaphniamL -1) Daphnia densities. In mesocosms, Daphnia was critical to the development of tadpoles: in the presence of Daphnia, tadpoles were twofold heavier at metamorphosis than in their absence. Daphnia and Bd interacted to affect the tadpole survival: survival was highest in the presence of Daphnia and in the absence of Bd. We were unable to detect an effect of Daphnia on the transmission of Bd in mesocosms. However, Bd transmission among the tadpoles in mesocosms was unexpectedly low, limiting our power to detect an effect of Daphnia on transmission. 5.Tadpole dissection showed that tadpoles also consumed large numbers of Daphnia. Current models of mesocosm food webs that assume no predation by tadpoles on zooplankton therefore probably overlook important features of both natural and experimental systems. © 2012 Blackwell Publishing Ltd.

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